Display device and driving method thereof

Abstract

A display device is provided, which includes: light emitting elements; switching transistors transmitting data signals in response to scanning signals; driving transistors, each driving transistor electrically connected to a driving signal line and one of the switching transistors and supplying a current to the light emitting elements in response to an output signal of the one of the switching transistors and the driving signal of the driving signal line; and a first capacitor electrically connected between each driving transistor and each driving signal line; and a second capacitor electrically connected between each light emitting element and each driving transistor, wherein the first and the second capacitors transmit the driving signal by capacitive coupling.

1. A display device comprising:
 a light emitting element; 
 a switching transistor which transmits a data signal in response to a scanning signal; 
 a driving transistor having an input terminal directly electrically connected to a driving signal line, a control terminal directly connected to a source or a drain of the switching transistor, and an output terminal directly connected to the light emitting element, the driving transistor configured to supply a current to the light emitting element in response to an output signal of the switching transistor and a driving signal of the driving signal line; and 
 a first capacitor directly connected between the control terminal of the driving transistor and the driving signal line; and 
 a second capacitor having a first terminal connected directly to the light emitting element and a second terminal connected directly to the control terminal of the driving transistor, 
 wherein 
 the first and the second capacitors transmit a voltage depending on the driving signal and capacitances of the first capacitor and the second capacitor to the control terminal of the driving transistor, 
 a single display frame is divided into three periods comprising a first period for writing data voltages, a second period for emitting light, followed by a third period for applying a reverse biasing voltage, 
 the driving signal includes a first voltage level which turns off the driving transistor in the first period, a second voltage level which turns on the driving transistor in the second period and a third voltage level less than the first voltage level and applied in the third period, and 
 the third voltage level applies a negative biased voltage to the control terminal of the driving transistor and the voltage of the control terminal of the driving transistor during the second period and the third period varies based on capacitive coupling of the first and second capacitors and the driving signal. 
 
   
   
     2. The display device of  claim 1 , wherein
 the first capacitor is electrically connected between the control terminal and the input terminal of the driving transistor, and 
 the second capacitor is electrically connected between the control terminal and the output terminal of the driving transistor. 
 
   
   
     3. The display device of  claim 2 , wherein the switching transistor and the driving transistor comprise amorphous silicon. 
   
   
     4. The display device of  claim 1 , wherein the switching transistor and the driving transistor comprise NMOS thin film transistors. 
   
   
     5. A display device comprising:
 a switching transistor; 
 a plurality of pixels, each pixel of the plurality of pixels including a light emitting element and a driving transistor which supplies current to the light emitting element, the driving transistor having an input terminal directly electrically connected to a driving signal line, a control terminal directly connected to a source or a drain of the switching transistor, and an output terminal directly connected to the light emitting element; 
 a signal controller which divides a single display frame into a first period for writing data voltages, a second period for emitting light and a third period for applying a reverse biasing voltage and which generates a control signal to control a duration of each of the first, second and third periods; and 
 a driving signal generator which supplies a driving signal in response to the control signal from the signal controller, the driving signal having three or more voltage levels that are different from each other, wherein 
 data voltages are written to each pixel during the first period, the driving transistor supplies current to the light emitting element to emit light based on data signals during the second period, 
 the driving transistor is supplied with a reverse bias during the third period, 
 a terminal of the light emitting element has a substantially fixed voltage, 
 the driving signal includes a first voltage level which turns off the driving transistor during the first period, a second voltage level which turns on the driving transistor during the second period and a third voltage level which is less than the first voltage level and which is applied during the third period, and 
 the third voltage level applies a negative biased voltage to the control terminal of the driving transistor and the voltage of the control terminal of the driving transistor during the second period and the third period varies based on capacitive coupling of a first capacitor, which is directly connected between the control terminal of the driving transistor and the driving signal line, and a second capacitor, which includes a first terminal connected directly to the light emitting element and a second terminal connected directly to the control terminal of the driving transistor, and the driving signal. 
 
   
   
     6. The display device of  claim 5 , further comprising a data driver for writing the data signals to each pixel. 
   
   
     7. The display device of  claim 6 , wherein the light emitting element emits light responsive to the current supplied by the driving transistor. 
   
   
     8. The display device of  claim 7 , wherein a luminance of light emitted by the light emitting element varies in response to an amount of the current supplied by the driving transistor. 
   
   
     9. The display device of  claim 8 , wherein
 the second period is subsequent and adjacent to the first period, and 
 the third period is subsequent and adjacent to the second period.